Synthesis, characterization of some new 1,2-disubstituted benzimidazole derivatives and investigation of their antioxidant properties

Due to the pharmacological and biological activities of benzimidazole and its derivatives in many fields, the benzimidazole core has become an indispensable structure for the development of new therapeutic agents. In this thesis, 14 novel 1,2-disubstituted benzimidazole derivative compounds were synthesized, characterized and antioxidant properties were investigated. In the first step, the treatment of 4,5-Dimethyl-1,2-phenylenediamine with imino ester compound which was synthesised according to Pinner method resulted in the formation of compound 1. Then, the reaction of compound 1 with ethylbromoacetate in the presence of K2CO3 produced ester derivative compound (2). In the next step, this ester (2) was converted to hydrazide derivative (3). Then, the teatment of hydradize derivative with several aldehydes gave Schiff based benzimidazole compounds (4a-d). The treatment of compound 3 with CS2 in the presence of KOH resulted in the formation of 1,3,4-oxadiazole-2-thiol compound (5). And the hydrazide compound (3) was also converted to the corresponding carbothioamide structures (6a,b). In the next step, the treatment of carbothioamide compounds (6a,b) with cold and concentrated H2SO4 produced 1,3,4-thiadiazol compounds (7a,b). In the final step, the cyclisation of the same intermediates (6a, b) in the presence of 2N NaOH produced 1,2,4-triazol compounds (8a,b). Also, the antioxidant properties of the synthesized compounds in this study were clarified using various in vitro antioxidant assays including CUPRAC, ABTS and DPPH assays. The structures of the synthesized compounds were identified by IR, 1H-NMR, 13C-NMR and mass spectroscopic methods.